The invention relates to heavy trailer suspensions and, more particularly, to a mechanism and suspension to improve the stability and handling performance for knuckle-boom loader trailers in off-road conditions.
Nowadays, conventional configurations of knuckle-boom loader trailers have a simple frame trailer with not only a relatively rudimentary and inexpensive suspension, but also—and in sharp contrast, with an expensive, heavy and tall knuckle-boom crane and operator cab mounted thereon. While the knuckle-boom crane and operator cab will probably only towed with the crane lowered, the height of the operator cab and lowered nevertheless present a relatively high center of gravity.
These current day, conventional configurations for a knuckle-boom loader trailer offer sparse axle-suspension options, namely, just two.                (1) The simplest option is where the axles are welded directly to the frame. However, this offers no travel-shock dampening, which thus can cause equipment damage when transporting the trailer from job-site to job-site; and        (2) An alternative and slightly improved option is a single-point suspension that rigidly attaches to a tandem axle set. This will offer suspension articulation front to back. But, single-point suspensions are limited to how sizable of bump obstacles that the suspension and trailer can (versus cannot) overcome.        
Both those kinds of suspensions for knuckle-boom loader trailers are further known as being difficult to maneuver in the off-road conditions where these trailers are put to use in logging environments. In southern logging fields, the soil is typically sandy and/or clay. The soil is furthermore rutted to deeply rutted by previous logging vehicle traffic. Tree limb and tree trunk parts litter the field everywhere, as well as stumps.
The knuckle-boom loader is typically the product of one manufacturer, while the trailer is typically the product of another. For example, “DEERE” ® is one typical example of a knuckle-boom loader manufacturer. “PITTS TRAILERS” ® is a typical example of a manufacturer of a trailer therefor. When a knuckle-boom loader is affixed on a trailer, this a permanent mounting, and results in a knuckle-boom loader trailer.
Knuckle-boom loader trailers might be towed over-the-road once during its use life, and that is from the dealer to the where the logging roads begin where the logging fields are. After that one-way trip from the dealer, knuckle-boom loader trailers are towed by heavy tractors, at very low speeds (ie., at a crawl at times, just a couple to a few miles per hour).
The knuckle-boom loader is an expensive piece of equipment (eg., hundreds of thousands of dollars), a heavy piece of equipment (eg., in excess of 50,000 lbs.), and therefore the tow speed is very slow.
It is an object of the invention to produce a suspension design which is more easily maneuverable in the field and would also be safer, have time saving benefits when transported, and can save potential costly losses by reducing if not eliminating costly equipment damage due to trailer rollover.
A number of additional features and objects will be apparent in connection with the following discussion of the preferred embodiments and examples with reference to the drawings.